The windows used in aerospace applications are one of the most demanding applications for the single crystal or polycrystalline ceramics. They must strongly withstand severe aero-thermal heating, thermal shock resistance, rain drop and sand erosion, etc. Among the most suitable materials characterized by high strength and reasonable thermal conductivity in combination with high optical transmission over a broad wavelength ranges are ZnS, ZnSe, sapphire, and spinel.
Multi-pane conformal aircraft optical windows reduce resolution at all fields of regard where a sensor free aperture spans two or more panes. Resolution is reduced due to optical path differences induced by window thickness differences, window incidence angle, window wedge angle, and index of refraction variation between the spanned panes. Window pane size is limited by the current state of the art for manufacture of multi-spectral window optical grade blanks.